1. Technical Field
This application relates to delivery of a vascular filter for capturing blood clots and more particularly to a cartridge containing a vein filter for mounting to a component of a delivery system.
2. Background of Related Art
Passage of blood clots to the lungs is known as pulmonary embolism. These clots typically originate in the veins of the lower limbs and can migrate through the vascular system to the lungs where they can obstruct blood flow and therefore interfere with oxygenation of the blood. Pulmonary embolisms can also cause shock and even death.
In some instances, blood thinning medication, e.g. anticoagulants such as Heparin, or sodium warfarin can be given to the patient. These medications, however, have limited use since they may not be able to be administered to patients after surgery or stroke or given to patients with high risk of internal bleeding. Also, this medication approach is not always effective in preventing recurring blood clots.
Therefore, surgical methods to reduce the likelihood of such pulmonary embolisms by actually blocking the blood clot from reaching the lungs have been developed. One surgical method of treatment involved major surgery where the size of the vessel lumen was restricted by placement of ligatures or clips around the vein, e.g. the inferior vena cava which transports blood from the lower portion of the body to the heart and lungs. This prevented passage of dangerously large blood clots through the vein to the lungs. However, this approach is an invasive surgical procedure, requiring an abdominal incision and general anesthesia and frequently causing vessel thrombosis and lower extremity swelling. Also, there is a lengthy patient recovery time and additional hospital and surgeon expenses associated with this major surgery. In fact, oftentimes, the patients requiring the surgery are unhealthy and the major surgery and general anesthesia poses a risk in and of itself.
To avoid such invasive surgery, less invasive surgical techniques have been developed. These involve the placement of a mechanical barrier in the inferior vena cava. These barriers are in the form of filters and are typically inserted through either the femoral vein (femoral approach) in the patient's leg or the arm or right jugular vein in the patient's neck (jugular approach) under local anesthesia. The filters are then deployed intravascularly in the inferior vena cava where they expand to block migration of the blood clots from the lower portion of the body to the heart and lungs.
Since numerous filters which can be inserted via both the femoral and jugular approaches have a filtering portion downstream of a mounting (anchoring) portion, the surgeon must ensure that the filter is placed in the correct orientation so that the filtering portion is positioned to capture blood clots. Insertion and placement in the wrong orientation would cause the filter to be inoperative and could cause thrombosis. With certain filters, the wrong orientation could result in the anchoring features of the filter failing to grasp the vessel, resulting in migration of the filter to the central venous vasculature which could cause obstruction, vessel perforation, dysrhythmia or even death.
One attempt to orient the filter in the proper position is the cartridge being marketed by Cordis for placement of its Optease* vena cava filter. The cartridge, which contains the filter inside, has arrows labeled jugular or femoral to designate the direction to attach via snap fit the cartridge to the delivery instrument. However, if improper attention is paid by the user to the arrows, the user could easily attach the cartridge to the delivery instrument in the incorrect orientation, causing the problems enumerated above.
B. Braun markets another cartridge for delivery of their Vena Tech* filter. The cartridge has a femoral end colored red and a jugular end colored blue. A corresponding red pusher and blue pusher are provided which can only fit into the respective ends of the cartridge. The selected pusher is intended to be inserted into the cartridge prior to mounting of the cartridge to the delivery instrument However, the surgeon can mistakenly mount the cartridge in the wrong orientation by threading the cartridge first onto the delivery system (in the wrong orientation), and then inserting the pusher.
In U.S. Pat. No. 6,328,755, a filter cartridge is disclosed with a hinged locking mechanism. Orientation of the cartridge is not addressed.
In commonly assigned co-pending patent application Ser. No. 10/889,429, filed Jul. 12, 2004, a cartridge is disclosed with a pair of locking rails engaged by a detent to hold the cartridge in place. Markings on the cartridge indicate the jugular or femoral orientation. However, this cartridge suffers from the disadvantages enumerated above since the surgeon must rely solely on the markings for cartridge orientation.
It would be advantageous to provide a filter cartridge which is easily mounted to a delivery system component and which reduces the chances of being loaded in the incorrect orientation. Such cartridge could advantageously be used to load various types of filters. It could also be used to load various vascular devices.